#include<iostream>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<sys/types.h>
#include<unistd.h>
#include<sys/wait.h>

#define COMMAND_SIZE 1024
#define FORMAT "[%s@%s %s]# "

//shell定义的全局数据

#define MAXARGC 128
char* g_argv[MAXARGC];
int g_argc = 0;

const char* GetUserName()
{
    const char *name  = getenv("USER");
    return name == NULL? "None":name;
}

const char* GetHostName()
{
    const char* hostname = getenv("HOSTNAME");
    return hostname == NULL? "None":hostname;
}

const char* GetPwd()
{
    const char* pwd = getenv("PWD");
    return pwd == NULL? "None":pwd;
}

//路径
std::string DirName(const char *pwd)
{
#define SLASH "/"
    std::string dir = pwd;
    if(dir == SLASH)return SLASH;
    auto pos = dir.rfind(SLASH);
    if(pos == std::string::npos)return "BUG?";
    return dir.substr(pos+1);
}

void MakeCommandline(char cmd_prompt[],int size)
{
    //snprintf(cmd_prompt,size,FORMAT,GetUserName(),GetHostName(),DirName(GetPwd()).c_str());
    snprintf(cmd_prompt,size,FORMAT,GetUserName(),GetHostName(),GetPwd());
}

void PrintfCommandPrompt()
{
    char prompt[COMMAND_SIZE];
    MakeCommandline(prompt,sizeof(prompt));
    printf("%s",prompt);
    fflush(stdout);
}

bool GetCommandLine(char *out,int size)
{

    char *c = fgets(out,size,stdin);
    if(c == NULL)return false;
    out[strlen(out)-1] = 0;
    if(strlen(out) == 0) return false;
    return true;
}

bool CommandPrase(char* commandline)
{
#define SEP " "
    g_argc = 0;
    //命令行分析
    g_argv[g_argc++] = strtok(commandline,SEP);
    
    while((bool)(g_argv[g_argc++] = strtok(nullptr,SEP)));
    return true;
}

void PrintArgv()
{
    for(int i=0;g_argv[i];i++)
    {
       printf("argv[%d]->%s\n",i,g_argv[i]); 
    }
    printf("argc->%d\n",g_argc);
}

int Execute()
{

    //4.执行命令
    pid_t id = fork();
    if(id==0)
    {
        //child
        execvp(g_argv[0],g_argv);
        exit(1);
    }
    //father
    pid_t rid = waitpid(id,nullptr,0);
    (void)rid;
    return 0;
}

int main()
{
    while(true)
    {
        //1.输出命令行提示符
        PrintfCommandPrompt();
        //2.获取用户输入的命令
        char commandline[COMMAND_SIZE];
        if(GetCommandLine(commandline,sizeof(commandline)))
            continue;
        //3.命令行分析
        CommandPrase(commandline);
        
        //4.执行命令
        Execute();
    }
    return 0;
}
